1. Field of the Invention
The present invention relates to a microdrill bit of tungsten carbide based cemented carbide which has a high wear resistance and is less susceptible to fracturing.
2. Prior Art
Prior art microdrill bits have been made of a tungsten carbide (WC) based cemented carbide which contains about 1.0% by weight of tantalum carbide (TaC) for preventing grain growth of tungsten carbide (WC) in a hard dispersed phase and about 6% by weight of a cobalt alloy comprised of a solid solution of cobalt (Co) with tungsten.
The aforesaid prior art microdrill bits have been susceptible to fracturing. Therefore, cobalt content in the cemented carbide may be increased to enhance the fracture resistance characteristics. However, a simple increase in the cobalt content results in an undue lowering of the wear resistance of the microdrill bits. Thus, the development of a new cemented carbide for microdrill bits, which exhibits not only a great fracture resistance but also a high wear resistance, has long been desired.